Facebook announced this week that it added its 200 millionth user on April 8, 2009. The US had more Facebook users than any other country. However, the largest concentration of users was in the Eastern US and Western Europe.
In Q1 of this year, the fastest-growing segment of the US Facebook population was people ages 26 to 44, and other countries will undoubtedly follow that path. See our earlier post on this called the Graying of Facebook.